Introduce {left,right}PositionOf() for VisiblePosition

Source/core/editing/VisiblePosition.h

Index: Source/core/editing/VisiblePosition.h
diff --git a/Source/core/editing/VisiblePosition.h b/Source/core/editing/VisiblePosition.h
index 2e107c06838de136b4adaeaa04d6c9535e86f552..6cca7d9fc072c1e06f7a64e9c6ad7057fbd4d9a8 100644
--- a/Source/core/editing/VisiblePosition.h
+++ b/Source/core/editing/VisiblePosition.h
@@ -100,10 +100,7 @@ public:
     VisiblePosition skipToStartOfEditingBoundary(const VisiblePosition&) const;
     VisiblePosition skipToEndOfEditingBoundary(const VisiblePosition&) const;
 
-    VisiblePosition left() const;
-    VisiblePosition right() const;
-
-    // FIXME: This does not handle [table, 0] correctly.
+    // TODO(yosin) This does not handle [table, 0] correctly.
     Element* rootEditableElement() const { return m_deepPosition.isNotNull() ? m_deepPosition.anchorNode()->rootEditableElement() : 0; }
 
     // Rect is local to the returned layoutObject
@@ -123,9 +120,6 @@ private:
     template<typename Strategy>
     void init(const PositionAlgorithm<Strategy>&, TextAffinity);
 
-    Position leftVisuallyDistinctCandidate() const;
-    Position rightVisuallyDistinctCandidate() const;
-
     Position m_deepPosition;
     TextAffinity m_affinity;
 };
@@ -139,6 +133,11 @@ int lineDirectionPointForBlockDirectionNavigationOf(const VisiblePosition&);
 
 EphemeralRange makeRange(const VisiblePosition&, const VisiblePosition&);
 
+// TODO(yosin) We should move |leftPositionOf()| and |rightPositionOf()| to
+// "VisibleUnits.cpp".
+VisiblePosition leftPositionOf(const VisiblePosition&);
+VisiblePosition rightPositionOf(const VisiblePosition&);
+
 CORE_EXPORT Position canonicalPositionOf(const Position&);
 CORE_EXPORT PositionInComposedTree canonicalPositionOf(const PositionInComposedTree&);
 // TODO(yosin) We should move |characterAfter()| and |characterBefore()| to